Exothermic manganese addition agent



United States Patent Walter Crafts, Niagara Carbide (Iorporation,

No Drawing. Application May 12, 1954, Serial No. 429,363

3 Claims. (Cl. 75-27) Falls, N. Y., assignor to Union a corporation ofNew York This invention relates to improved exothermic reactionmixtures, and more particularly concerns exothermic manganese additionagents for a ferrous melt.

The big problem in adding manganese metal to a steel or cast iron bathis finding improved means for recovering manganese values in the melt.The addition of manganese in furnace baths is already a problem, a largeand uncertain amount of the alloying element being lost as a result ofoxidation. Ladle additions are more satisfactory, but further diflicultyis encountered in adding manganese alloy because of the heat absorbed indissolving the cold manganese addition. This absorption of heat by themanganese alloy addition reduces the temperature of the metallic bath,and the resulting temperature drop, if substantial enough, may in turncause the segregation of important alloying ingredients. Suchtemperature drop will also increase skull formation.

It has been known for some time that the temperature drop thataccompanies the addition of alloying elements to a steel melt may bereduced to an appreciable extent by the addition of reaction materialshaving exothermic properties. In the production of steel alloys usingsuch materials, the usual practice is to add an exothermic mixtureincluding the alloying materials to a steel or cast iron melt, and to soproportion the constituents of the exothermic mix that the heatgenerated is sufficient to substantially reduce the amount of chill thatwould otherwise result from such alloy addition. The usual exothermicmix consists essentially of an oxidizing agent, a reducing agent, andone or more alloying metals. A common oxidizing agent that is widelyused is sodium nitrate, and the reducing agent is silicon.

One of the difiiculties inherent in a reaction mixture containing sodiumnitrate as oxidizing agent, silicon as reducing agent, and an additionof manganese alloy is the violence of the exothermic reaction. Theexplosive nature of the exothermic reaction causes part of the manganesealloy content to be hurled outside the ladle and, as a consequence,reduces considerably the recovery of available manganese. And too, theheat of the reaction is dissipated to the atmosphere rather thantransferred to the metal.

In order to improve the recovery of manganese values in a silicon-sodiumnitrate exothermic mixture, control over the exothermic reaction isessential. To eifect this control, the violence of the exothermicreaction must be reduced. At the same time, the stabilization of theexothermic reaction must not proceed so far as to jeopardize thefulfillment of the exothermic function by either chilling the moltenbath or decreasing the rate of dissolution of the manganese alloyingaddition.

It is, therefore, an important object of the present invention tointroduce manganese additions to molten steel in the form of anexothermic mixture containing silicon and sodium nitrate to overcome theobjectionable effects isted above, without reducing to any significantdegree the rate of solution of the manganese addition, thereby elfectingmaximum recovery of the manganese available in the exothermic mixture.

Another object of the present invention is to provide amanganese-containing exothermic mix for a steel melt, the mix having arelatively high proportion of manganese content, and characterized by amore complete recovery of manganese than has heretofore been possible bythe use of nonexothermic manganese addition agents.

A further object of the present invention is to provide in an exothermicmixture including silicon and sodium nitrate, an oxidizing agent forfacilitating the incorporation of manganese values in a steel melt, themixture being capable of evolving sufficient heat for effecting rapidsolution of the manganese early in the tap to promote uniformdistribution therein.

In manganese addition agents containing silicon and sodium nitrate asexothermic reactants, the violence with which heat is released isundesirable, particularly in steel operations. The low recovery ofavailable manganese in the exothermic mixture due to the turbulence ofthe exothermic reaction, and the hazardous conditions created thereby,are but some of the conditions that require remedial action. The presentinvention provides improved means for obviating the above defects. Thisis accomplished by including in the exothermic mixture a moderatingagent to reduce the turbulent behavior of the exothermic reactants.

It has been found that the undesirably violent eruptions that take placeupon the ignition of a reaction mixture of the silicon-sodium nitratetype in a steel bath may be substantially eliminated by introducing intothe reaction mixture a moderating agent consisting of oxidic ores ofiron and manganese, for example FezOs and M1102. Yet sufficiently rapidrates of reaction and of assimilation of the available manganese in theaddition agent are maintained, and temperature drop due to the additionof the mixture is not excessive.

Accordingly, the exothermic reaction mixture of the present inventioncomprises sodium nitrate as oxidant, silicon as reducing agent, one ormore manganese alloy additions, and as a moderator, iron ore andmanganese ore. Preferably the silicon and the manganese content arepresent in the subject mixture as constituents of an alloy, for example,silico-manganese.

According to the present invention, the iron ore and manganese orepresent in the subject mixture serve not only to reduce the turbulenceof the exothermic reaction, but also serve in the capacity of oxidantsfor exothermic reaction with part of the silicon present in the mixture.Following are some of the main exothermic reactions which account inlarge measure for the reduction in chill during the alloying operation:

Other side reactions which also occur during ignition of the reactionmix, and which contribute to the exothermicity thereof are:

The above formulas are based upon the use of stoichiometric proportionsof sodium nitrate, iron ore and manganese ore as oxidants, and, asreducing agent, silicon. Thereby, the reducing agent is present insufficient quantity to substantially reduce the sodium nitrate and theoxidic ores of iron and manganese in the mix.

The oxides of manganese, iron and sodium, formed as a result of theabove reactions, are believed to form complex compounds or solutions inthe by-product silicabearing slag formed during the reaction.

In order that the invention may be more fully appreciat it may be notedat this point that exothermic reaction mixtures containing silicon,sodium nitrate and manganese behave dilferently when either iron ore ormanganese ore is employed as the oxidic moderating agent. For instance,individual experiments show that while iron is successful in inhibitingthe activity of the exothermic mixture, it is not altogethersatisfactory from a standpoint of efliciency since much of the siliconis recovered in the steel melt. This might be due to only partialreaction of the iron ore with the silicon and reaction with themanganese as well since part of the manganese is oxidized and lost asslag, thereby depriving the steel of its intended alloying ingredient. nthe other hand, manganese ore alone acts to improve beneficially themanganese recovery, with little or no silicon absorbed by the steel.However, the solution time of the manganese addition in the steel meltis lengthened.

Combining the iron ore and manganese ore into the reaction mixtureserves to utilize the accelerating effect of the iron ore for fastsolution rate of the manganese addition and the excellent manganeserecovery feature of the manganese ore.

In order to indicate still more fully the nature of the presentinvention, results of tests showing the effects of manganese ore andiron ore, either individually or in combination with each other, inmanganese addition agents containing silicomanganese and sodium nitrateare tabulated below in Table I, it being understood that these tests arepresented as illustrative only, and that they are not intended to limitthe scope of the invention. The data reported in Table I are the resultsof a series of tests in which a suflicient quantity of manganeseaddition agent was added to a 100 pound bath of molten steel to raisethe manganese content of the steel 1%, the bath being at a temperatureof about 1600 C.

Table I Temper- Percent Percent Composition of Exonture SolutionIndicated Indicated thermic Addition Agent Drop Time, Mon Silicon 0.seconds ganese Recovery Recovery 68.5% SiMn, 9% N eNOa, 22%

Mn ore 7 55 100 28 68.5% SiMn, 14% NaNO 17% Fe Ore, 0.5% Mogul Binder .t7 74 47 68.5% SlMn, 14% NBNOs,

17% Mn ore 6 50 100 28 68.5% SlMn, 14% NaN 0;,

15% Mn ore, 2.5% Fe ore... 5 45 89 9 68.5% SlMn, 14% N aN 0:,

12.5% Mn ore, 5% Fe ore. 6 91 nil 68.5% SiMn, 17% NaN 0:,

9.5% Mn ore, 5% Fe ore 0 33 83 9 68.5% SlMn, 19% NaN0;,

12% Mn ore B 60 104 nil The above table demonstrates that the employmentof iron ore alone in exothermic mixes containing silicon and sodiumnitrate results in relatively good solution time (25 seconds),relatively poor manganese recovery (74% and relatively high siliconrecovery (47%). With only manganese ore in the mixture, manganeserecovery is at a maximum (100%), silicon recovery fair (28%), andsolution time, about one minute. Tests employing both manganese ore andiron ore exhibited relatively high indicated manganese recoveriesamounting to 83% or better and solution times of 45 seconds or less.Silicon recoveries in the melt amounted to less than 10%, and in someinstances were present only as traces.

It will be noted from the above table that the composition range of thereaction mixture embodying the principles of the present invention maybe varied over a considerable range without impairing its exothermicprop erties. Best results are obtained when the percentages of theconstituents of the instant exothermic mixture lie within thecomposition range listed below in Table II. The analysis of theconstituents in Table II is typical.

Table II M nximum Preferred Optimum results are obtained when the ratioof manganese ore to iron ore is between 2.5 to 1.0 and 6.0 to 1.0.

In practicing the invention, sodium nitrate is admixed with suificientamounts of silicomangane-se alloy, iron ore and manganese ore to producean exothermic alloy addition agent containing at least 45% availablemanganese. The ingredients of the mixture are preferably of mesh size(i. e., capable of passing through a screen having 0.147 mm. openings),with the exception of the sodium nitrate which is of 48 mesh size (0.295mm. openings). The mix of the invention may then be applied to the meltin either bonded or unbonded form. In the present instance, the additionagent is added in the form of pellets made by compacting the powderedmixture at approximately 2000 p. s. i. A slight amount of water may beadded.

Incorporation of the mixture into the steel melt in an amount equivalentto 1% Mn results in average temperature drop of less than 8 C., anaverage solution time of less than 45 seconds, and negligible siliconrecoveries. Manganese recoveries, amounting to as high as 91% confirmthe acceptability of the instant mix. Tests show that the availablemanganese recovered in the melt is distributed uniformly throughout themelt.

It will be understood that modifications and variations may be effectedwithout departing from the novel concepts of the present invention.

What is claimed is:

1. An addition agent for a ferrous melt comprising 9.0% to 20.0%manganese ore, 2.0% to 9.0% iron ore, 10% to 20% sodium nitrate,remainder silicomanganese alloy, and characterized by fast solutionrate, relatively high manganese recovery and relatively high exothermicity.

2. An addition agent for ferrous melt comprising 12% to 20% iron ore andmanganese ore, the proportion of said manganese ore to said iron orebeing between 2.5 to 1.0 and 6.0 to 1.0, 10% to 20% sodium nitrate,remainder silicomanganese, and characterized by relatively highmanganese recovery in the melt, fast solution rate and relatively highexothermicity.

3. An addition agent for a ferrous melt comprising 9.0% to 20% oxidicmanganese ore, 2.0% to 9.0% oxidic iron ore, 10% to 20% sodium nitrate,remainder silicomanganese alloy, the proportion of said manganese ore tosaid iron ore being between 2.5 to 1.0 and 6.0 to 1.0.

References Cited in the file of this patent UNITED STATES PATENTS1,431,621 Benekcr Oct. 10, 1922 1,623,757 Saklatwalla Apr. 5, 19271,820,998 Becket Sept. 1, 1931 2,243,784 Udy May 27, 1941 2,367,630 UdyJan. 16, 1945

1. AN ADDITION AGENT FOR A FERROUS MELT COMPRISING 9.0% TO 20.0%MANGANESE ORE, 2.0% TO 9.0% IRON ORE, 10% TO 20% SODIUM NITRATE,REMAINDER SLICOMANGANESE ALLOY, AND CHARACTERIZED BY FAST SOLUTION RATE,RELATIVELY HIGH MAGANESE RECOVERY AND RELATIVELY HIGH EXOTHERMIICITY.